1. Field of the Invention
The present invention relates to novel galectins. More specifically, isolated nucleic acid molecules are provided encoding human galectin 8, 9, 10, or 10SV. Galectin 8, 9, 10 and 10SV polypeptides are also provided, as are vectors, host cells and recombinant methods for producing the same. The invention further relates to screening methods for identifying agonists and antagonists of galectin 8, 9, 10, or 10SV activity. Also provided are diagnostic methods for detecting cell growth disorders and therapeutic methods for cell growth disorders, including autoimmune diseases, cancer, and inflammatory diseases.
2. Related Art
Lectins are proteins that bind to specific carbohydrate structures and can thus recognize particular glycoconjugates. Barondes et al., J. Biol. Chem. 269(33):20807-20810 (1994). Galectins are members of a family of xcex2-galactoside-binding lectins with related amino acid sequences (For review see, Barondes et al., Cell 76:597-598 (1994); Barondes et al., J. Biol. Chem. 269(33):20807-20810 (August 1994)). Galectin 1 (aka. L-14-1, L-14, RL-14.5, galaptin, MGBP, GBP, BHL, CHA, HBP, HPL, HLBP 14, rIML-1) is a homodimer with a subunit molecular mass of 14,500 which is abundant in smooth and skeletal muscle, and is present in many other cell types (Couraud et al., J. Biol. Chem. 264:1310-1316 (1989)). Galectin 2 was originally found in hepatoma and is a homodimer with a subunit molecular weight of 14,650 (Gitt et al, J. Biol. Chem. 267:10601-10606 (1992)). Galectin 3 (aka. Mac-2, EPB, CBP-35, CBP-30, and L-29) is abundant in activated macrophages and epithelial cells and is a monomer with an apparent molecular mass between 26,320 and 30,300 (Cherayil et al., Proc. Natl. Acad. Sci. USA 87: 7324-7326 (1990)). Galectin 4 has a molecularmass of 36,300 and contains two carbohydrate-binding domains within a single polypeptide chain (Oda et al., J. Biol. Chem. 268:5929-5939 (1993)). Galectins 5 and 6 are mentioned in Barondes et al., Cell 76:597-598 (1994). Human galectin 7 has a molecular mass of 15,073 and is found mainly in stratified squamous epithelium (Madsen et al., J. Biol. Chem. 270(11):5823-5829 (1995)).
Animal lectins, in general, often function in modulating cell-cell and cell-matrix interactions. Galectin 1 has been shown to either promote or inhibit cell adhesion depending upon the cell type in which it is present. Galectin 1 inhibits cell-matrix interactions in skeletal muscle (Cooper et al., J. Cell Biol. 115:1437-1448 (1991)). In other cell types, galectin 1 promotes cell-matrix adhesion possibly by cross-linking cell surface and substrate glycoconjugates (Zhou et al., Arch. Biochem. Biophys. 300:6-17 (1993); Skrincosky et al., Cancer Res. 53:2667-2675 (1993)).
Galectin 1 also participates in regulating cell proliferation (Wells et al., Cell 64:91-97 (1991)) and some immune functions (Offner et al., J. Neuroimmunol. 28:177-184 (1990)). Galectin 1 has been shown to regulate the immune response by mediating apoptosis of T cells (Perillo et al., Nature 378:736-739 (1995)).
Galectin 3 promotes the growth of cells cultured under restrictive culture conditions (Yang et al., Proc. Natl. Acad. Sci. USA 93:6737-6742 (June 1996)). Galectin 3 expression in cells confers resistance to apoptosis which indicates that Galectin 3 could be a cell death suppressor which interferes in a common pathway of apoptosis. Id.
Accordingly, there is a need in the art for the identification of novel galectins which can serve as useful tools in the development of therapeutics and diagnostics for regulating immune response.
The present invention provides isolated nucleic acid molecules comprising a polynucleotide encoding the galectin 8, 9, 10, or 10SV polypeptide having the amino acid sequence is shown in FIGS. 1, 2A-2B, 3A-3B, and 4A-4B, respectively (SEQ ID NOs:2, 4, 6, and 8, respectively) or the amino acid sequence encoded by the cDNA clones deposited as ATCC Deposit Numbers 97732, 97733 and 97734 on Sep. 24, 1996.
The present invention also relates to recombinant vectors, which include the isolated nucleic acid molecules of the present invention, and to host cells containing the recombinant vectors, as well as to methods of making such vectors and host cells and for using them for production of galectin 8, 9, 10, or 10SV polypeptides or peptides by recombinant techniques.
The invention further provides an isolated galectin 8, 9, 10, or 10SV polypeptide having an amino acid sequence encoded by a polynucleotide described herein.
The present invention also provides a screening method for identifying compounds capable of enhancing or inhibiting a cellular response induced by galectin 8, 9, 10, or 10SV, which involves contacting cells which express galectin 8, 9, 10, or 10SV with the candidate compound, assaying a cellular response, and comparing the cellular response to a standard cellular response, the standard being assayed when contact is made in absence of the candidate compound; whereby, an increased cellular response over the standard indicates that the compound is an agonist and a decreased cellular response over the standard indicates that the compound is an antagonist.
In another aspect, a screening assay for agonists and antagonists is provided which involves determining the effect a candidate compound has on galectin 8, 9, 10, or 10SV binding to the xcex2-galactosidase sugar. In particular, the method involves contacting the xcex2-galactosidase sugar with a galectin 8, 9, 10, or 10SV polypeptide and a candidate compound and determining whether galectin 8, 9, 10, or 10SV binding to xcex2-galactosidase sugar is increased or decreased due to the presence of the candidate compound.
The invention provides a diagnostic method useful during diagnosis disorder.
An additional aspect of the invention is related to a method for treating an individual in need of an increased level of galectin 8, 9, 10, or 10SV activity in the body comprising administering to such an individual a composition comprising a therapeutically effective amount of an isolated galectin 8, 9, 10, or 10SV polypeptide of the invention or an agonist thereof.
A still further aspect of the invention is related to a method for treating an individual in need of a decreased level of galectin 8, 9, 10, or 10SV activity in the body comprising, administering to such an individual a composition comprising a therapeutically effective amount of a galectin 8, 9, 10, or 10SV antagonist.